*2.6. Transparency and Color Parameters*

Transparency and color parameters are important factors as they affect the visual appearance, freshness, and quality parameters of food products. In the current study, the SA–AG composite hydrogel films incorporated with the CEO were examined for transparency and color parameters, including Lightness (L), a\*, b\*, and delta E. The addition of oil had a significant impact on the transparency of the films (Table 2). The transparency decreased from 79 to 21% with the addition of oil; the maximum was observed in the control (AC-1) and the minimum was shown by the AC-4 sample, which contained the maximum concentration of the CEO. The results of the current study are in accord with the findings of a previous study, in which the transparency of starch-based films decreased with the addition of oregano and black cumin essential oil [26].

**Table 2.** Transparency and color parameters of SA–AG hydrogel-based films.


Means carrying the same letters are significantly identical (*p* > 0.05). L: lightness, a\*: green-red color, b\*: blueyellow color, ∆E\*: overall color variation.

The SA–AG based films showed a slight decrease in Lightness (L), from 96.05 to 91.64%, with the addition of oil. The b\* value of the films varied from 0.94 to 4.97, whereases the a\* value ranged from 0.08 to 0.26. As mentioned in Table 2, the films showed (b\*) yellowness as the concentration of the CEO increased, with a maximum b\* value (4.97) in the AC-4 sample. The significant variation of ∆E values (0.85–5.04) also validates the overall color alterations in the films with the addition of oil. Essential oils contain a complex mixture of polyphenolic components that tends to absorb light, which can ultimately impact the color attributes of the film. Zhou et al. [20] reported a similar behavior in which the color of the cassava starch-based films changes to yellow with the addition of cinnamon essential oil. Furthermore, Tongnuanchan et al. [28] and Atarés et al. [29] reported similar results.
